arXiv subjects

Ankur Dey

Publications and source records attributed to Ankur Dey.

8 recordsLinked to original sources

arXiv2026

Defects extremal surfaces and interface CFTs

We propose a generalization of the defect extremal surface (DES) prescription to holographic interface conformal field theories (ICFTs), extending its applicability beyond the AdS$_3$/BCFT$_2$ framework. We consider a holographic ICFT$_2$ comprising two CFT$_2$s coupled across an interface, dual to two asymptotically AdS$_3$ geometries joined by a codimension-one end-of-the-world (EOW) brane. In the corresponding effective lower-dimensional description obtained via partial dimensional reduction on the brane-boundary combination, the theory on the brane is coupled to gravity, thereby enabling the computation of fine-grained entanglement entropy via the island formula. We demonstrate that the generalized DES prescription exactly reproduces the effective lower-dimensional results for finite subsystems in time-independent scenarios in the large brane tension limit, corresponding to weak gravitational coupling on the EOW brane. We further compute the entanglement entropy of semi-infinite bipartite pure states in radiation subsystems coupled to $2d$ eternal black holes, and obtain the corresponding Page curves.

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arXiv2026

Kerr-de Sitter Black Holes: Quantum Aspects and Cosmic Censorship Conjecture

In this article, we test the validity of the weak cosmic censorship conjecture (wCCC) in the background of a quantum Kerr-de Sitter (qKdS) black hole, incorporating exact backreaction from quantum matter fields. Using a test particle approach, we analyze whether an extremal qKdS black hole can be over-extremized to expose a naked singularity. Our results indicate that the black hole remains stable against horizon-destroying processes induced by infalling matter. Quantum corrections enhance the horizon's robustness rather than destabilize it, offering further evidence that wCCC remains preserved in the presence of quantum effects.

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arXiv2025

Holographic Entanglement Entropy in Janus deformed AdS$_3$ Geometries

We investigate the time dependent entanglement entropy for boosted single intervals in interface conformal field theories (ICFT$_2$s) dual to Janus deformed AdS$_3$ geometries. For a Janus deformed Poincar\'e AdS$_3$ background, we obtain the entanglement entropy and a Janus induced correction using a replica technique for the equivalent dual field theory described on a conformally flat background on corresponding AdS$_2$ slices on the asymptotic boundary. The holographic entanglement entropy is then computed through certain embedding relations for the bulk Janus deformed AdS$_3$ geometry which exactly match with the field theory results. We further extend our analysis to investigate the entanglement entropy of corresponding intervals in ICFT$_2$s dual to bulk Janus deformed BTZ black hole and AdS$_3$ black string geometries obtaining consistent results from both the field theoretic and bulk computations.

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arXiv2025

Entanglement, defects, and $T\bar{T}$ on a black hole background

In this article, we investigate the proposed duality between the island and the defect extremal surface (DES) prescriptions using the fine-grained entanglement entropy in Karch-Randall (KR) brane-world models with gravitating radiation baths. We consider the AdS$_3$ black string geometry and compute the entanglement entropy for radiation subsystems on an AdS$_2$ eternal black hole background using both the island and the DES prescriptions. We find an agreement between the two proposals for the island and the no-island phases, thus verifying the validity of the proposed duality. We further extend to a $T\bar{T}$ deformed AdS$_3$ black string geometry with a cut-off and find consistent results for both phases. We finally plot and compare the Page curves for the undeformed and deformed scenarios, and discuss the modifications due to $T\bar{T}$ deformation.

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arXiv2025

Holographic Reflected Entropy: Islands and Defect Phases

We investigate the mixed state entanglement structure through the reflected entropy for disjoint radiation subsystems coupled to a 2d eternal brane world black hole in a time dependent defect AdS$_3$/BCFT$_2$ scenario. Utilizing the island prescription and the defect extremal surface (DES) formula, we demonstrate a complex mixed state entanglement structure through the reflected entropy corresponding to distinct entanglement entropy phases. In each case we verify the holographic duality of the reflected entropy with the bulk entanglement wedge cross section (EWCS) and also obtain the Page curves for both the entanglement entropy and the associated reflected entropy phases. Furthermore, we extend our analysis to adjacent radiation subsystems and obtain consistent results using both the island and the DES prescription.

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arXiv2024

Bridging Boundaries: $T\bar{T}$, Double Holography, and Reflected Entropy

We investigate the reflected entropy for bipartite mixed state configurations in a $T\bar{T}$ deformed boundary conformal field theory in $2$ dimensions (BCFT$_2$). The bulk dual is described by asymptotically AdS$_3$ geometries with the cut off surface pushed deeper into the bulk and truncated by an end of the world brane. We obtain the reflected entropy up to a linear order in the radial cut-off for static and time dependent configurations involving an eternal black hole, from the island and defect extremal surface (DES) prescriptions in the context of the deformed AdS/BCFT. We observe agreement of the leading order correction for all cases between the two prescriptions. We also obtain the analogous of the Page curves for the reflected entropy and investigate the modification due to the $T\bar{T}$ deformation.

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arXiv2023

Odd entanglement entropy in $\text{T}\bar{\text{T}}$ deformed CFT$_2$s and holography

We construct a replica technique to perturbatively compute the odd entanglement entropy (OEE) for bipartite mixed states in $\text{T}\bar{\text{T}}$ deformed CFT$_2$s. This framework is then utilized to obtain the leading order correction to the OEE for two disjoint intervals, two adjacent intervals, and a single interval in $\text{T}\bar{\text{T}}$ deformed thermal CFT$_2$s in the large central charge limit. The field theory results are subsequently reproduced in the high temperature limit from holographic computations for the entanglement wedge cross sections in the dual bulk finite cut-off BTZ geometries. We further show that for finite size $\text{T}\bar{\text{T}}$ deformed CFT$_2$s at zero temperature the corrections to the OEE are vanishing to the leading order from both field theory and bulk holographic computations.

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arXiv2023

Covariant odd entanglement entropy in AdS$_3$/CFT$_2$

We advance a covariant construction for the holographic odd entanglement entropy (OEE) of time dependent bipartite states in CFT$_2$s dual to bulk AdS$_3$ geometries. In this context we obtain the OEE for bipartite states in zero, finite temperature and finite size CFT$_2$s dual to bulk pure AdS$_3$ and BTZ black hole geometries through appropriate replica techniques. The replica technique results for the time dependent OEE are reproduced modulo constants in the large central charge limit through holographic computations involving the bulk entanglement wedge cross section (EWCS). Subsequently we obtain the time dependent OEE for bipartite states in zero and finite temperature CFT$_2$s with a conserved charge dual to bulk extremal and non-extremal rotating BTZ black holes through both field theory and covariant holographic computations which again match up to constants in the large central charge limit.

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